The present invention relates to stirrup reinforcement for concrete pipe or other concrete products. Stirrup reinforcement comprises a plurality of wire projections extending out of the plane of the base welded wire fabric reinforcement. In concrete pipe, for example, the generally cylindrical cage might have stirrup reinforcements projecting radially from the cage in the vicinity of the crown and invert reinforcing portions thereof.
For many years in the concrete pipe industry, it was common practice to weld or otherwise secure individual lengths of wire to the base fabric on the job site, after the fabric had been shaped into a cylindrical cage. Another alternative was to weld a continuous sinusoidal stand of wire to the cylindrical cage such that the nodes of the strand projected radially from the welded wire reinforcing cage.
I pioneered various types of mats which include a plurality of base wires joined by several tie wires lying generally in the same plane as the base wires, and a plurality of short lengths of wire which comprise projections welded to the base wires so as to project out of the plane of the base wires and tie wires. Such mats can readily be inserted into the pipe reinforcing cage or the like with the stirrup projections projecting through the spaces in the reinforcing cage.
The stirrup projections are often bent near the top thereof so that the top portions extend generally laterally from the generally vertical legs of the projections. An elevational view of a segment of two stacked stirrup mats hving such projection is shown in FIG. 5 of the drawings. The lateral tops give additional strength to the concrete product in which they are embedded, beyond the strength which would be obtained if the stirrup projections were merely straight.
Unfortunately, such stirrup projections cause shipping and handling problems. The lateral tops on the projections cause the mats to get tangled when one tries to separate a stack of them. The base wires of one mat tend to interfere with the lateral tops of the stirrup projections of the next lower mats when one tries to lift them off. This is illustrated by the phantom arrows in FIG. 5. Further, the height of the stack becomes limited due to this interference and one ends up with a plurality of separate stacks where it would be more desirable to have a single stack.